My 5 week old baby is having a hard time pooping. He is formula fed and we have switched his formula three times. The last time we changed it seemed to work, but now 3 weeks later he's having a hard time again. He seems to be struggling by kicking and flailing around. He screams and his face turns red. He's been doing this since he woke up. It's been over 24 hours since he pooped last.I've tried using the thermometer trick but that didn't work either. I can't stand to see my baby in pain, any tips or advice?? He's on the Nutramigen formula.